While the initial benefit to the Team of estimating is in understanding their capacity to deliver value, there are in fact other benefits of estimating to the Team:
Clarity: Teams understand the type of work they do and what the market is asking for. They can ask clarifying questions to make acceptance criteria detailed enough for them implement the work. Through discussion as a result of estimation there is increased clarity for the whole Team.
Knowledge transfer. Team members explain the actual work helping the whole Team learn cross functional knowledge which, when coupled with paired work, prepare them to execute new skills on their own. As Teams participate in the estimation process, each skill set brings their viewpoint to the discussion, thus building a common understanding of the need and the work involved. Sure the person doing the change might think it is a simple change, but the person with the testing background might understand that there is a wider impact.
Reduced batch size: Estimation helps us forecast work. But what is interesting is that Teams quickly discover (as they analyze the success of their estimation) that the smaller the work, the more predictable their ability to deliver. So the process of estimation actually works to encourage smaller batches of work. Teams will start to establish team norms to say, for example, “if a story takes is expected to take more than 1/2 a week, we need to split it.”
I like this quote from Steve McConnell:
“The point of estimation is not to predict the future but to understand if we are even within a chance of managing our way to success.”
The business view of this “chance” is the forecast use of capacity. The Team / Team-of-Teams (Train) view of this is to work to their capacity.